Welcome to the July 2015 REBELCast, where Swami, Matt, and I are going to talk oxygen. It is important to remember that oxygen is a drug, and just like any drug we prescribe to patients it has potential side effects. Although there is a paucity of clinical trial data to support routine use of supplemental oxygen, most health care providers still put oxygen on patients for possible physiological benefits. So with that introduction today we are going to specifically tackle:

Background #1: The first report for supplemental oxygen for angina was in 1900, and since then, oxygen therapy has been a commonly used treatment of patients with ST-Elevation Myocardial Infarction (STEMI). The reason for this is the belief that supplemental oxygen will increase oxygen delivery to ischemic myocardium and help reduce myocardial injury. This belief is based off lab studies and older clinical trials, but there have been other studies that suggest potential adverse physiologic effects of supplemental oxygen (i.e reduced coronary blood flow, increased coronary vascular resistance, and production of reactive oxygen species) causing vasoconstriction and reperfusion injury. Ultimately, there are no studies evaluating the effects of supplemental oxygen therapy involving STEMI patients who are undergoing percutaneous coronary intervention. Taking all this information together there is a lot of uncertainty over the utility of routine supplemental oxygen therapy in acute myocardial infarction with no clear recommendations in normoxic patients in the most recent American Heart Association (AHA) STEMI guidelines. Despite this most patients with acute STEMI still have supplemental oxygen administered.

Individuals involved with the delivery of oxygen therapy pre-hospital and in-hospital were not blinded to treatment, but 6 month follow up coordinator and investigators undertaking data analysis were masked to treatment assignment

Bottom Line #1: This study does not demonstrate any significant benefit of routine use of supplemental oxygen therapy for reducing myocardial infarct size, improving patient hemodynamics, or alleviating symptoms, but we still need some studies with clinical endpoints before changing practice.

Background #2: It is a well-known fact that Non-Invasive Positive Pressure Ventilation (NIPPV) reduces the need for intubation and mortality in patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) or cardiogenic pulmonary edema. The reason for this is a decrease in work of breathing and improvement of gas exchange. On the other hand in patients with acute hypoxemic respiratory failure the use of NIPPV with respect to intubation and mortality are conflicting. Thus far the literature does not conclusively support the use of NIPPV in patients with non-hypercapnic acute hypoxemic respiratory failure. Oxygen through HFNC can produce low levels of positive pressure ventilation due to the high flow rates, which may also decrease physiological dead space. To date, the effect of oxygen through HFNC on mortality and intubation rates of patients admitted to the intensive care unit (ICU) with acute hypoxemic respiratory failure has never been studied until now.

What They Did #2:

Prospective, Multicenter, Open-Label, Randomized, Controlled Trial from 23 ICUs in France and Belgium of patients without hypercapnia who had acute hypoxemic respiratory failure

Bottom Line #2: HFNC is non-inferior to NIPPV, in patients with hypoxemic respiratory failure, but further studies are needed to determine whether these initial findings of benefit are practice changing.

For More Details of the above Studies Checkout the July 2015 REBELCast Show Notes

hi salim
thanks again for the great review
some concerns about FLORALI trial
great review salim, as usual …

My concens about FOLRALI trial:

1. The standard mask flow is much lower compared to high-flow nasal cannula (HFNC); I believe that this is a bias, and Venturi mask should have been used instead

2. Why the authors did not chose to compare HFNC with CPAP that is as simple, and has been shown to increase oxygenation (1,2), and decrease ETI criteria (3); in this way they should have finally answered the question whether flow or PEEP count

3. Primary outcome was not met; ETI decreased significantly only in the subgroup with P/F ratio < 200; furthermore, crossover was allowed among interventions

4. The device is simple; however, hypoxemic patients are not. In other words, simple device does not mean simple patient. The need for high level monitoring and experience should be stressed

5. The commentary article stands 'HFNC saves lives' which actually was only a secondary endpoint, a misleading message for the community

Hello Roberto,
First of all thank you for reading and listening to the post and podcast respectively. I agree with your concerns about the FLORALI Trial. There was quite a bit of crossover in the trial as well with 26 pts (face-mask) and 14 pts in HFNC receiving “rescue therapy” which the authors defined as BiPAP. 70% of the patients in the “rescue therapy” group ended up requiring intubation.
I agree with you that hypoxemia is complex. If anything this should have been a study of patients with hypoxemia with pneumonia, because just over 70% of them had pneumonia with a significant portion with only a single lung affected. Also this study does not help us determine if HFNC or BiPAP is superior to early intubation in the emergency department.
Finally, the disease process needs to be evaluated in my opinion to determine what the purpose of your therapy is. For example a patient with asthma and hypoxemia may get better over the course of minutes to hours with appropriate medications, however a patient with complex multifocal pneumonia will take days before antibiotics will help. All these oxygen strategies are bridges until definitive therapy (i.e. bronchodilators, antibiotics, etc…) can take effect. In one case the therapies could take minutes to hours in the other it could take days. My point for bringing this up is that I am not sure we are doing patients a favor by prolonging there intubation in one case and transforming it from an urgent airway to a crash, emergent airway.
Bottom Line: Agree with you reservations about the study and appreciate you listing them here for everyone else to read.